#include<stdio.h>
#include<assert.h>

char* my_strstr(const char* str1, const char* str2)
{
	const char* s1 = str1;
	const char* s2 = str2;
	const char* p = s1;

	assert(str1 && str2);
	if (*str2 == '\0')return  str1;
	while (*p)
	{
		s1 = p;
		s2 = str2;
		while (*s1 == *s2 && *s1 && *s2)
		{
		
			s1++;
			s2++;
		}
		if (*s2 == '\0')
		{
			return (char*)p;
		}
		p++;
	}
	return NULL;
}
int main()
{
	char arr1[20] = "ABCDEFGH";
	char  arr2[20] = "CDE";
	printf("%s", my_strstr(arr1, arr2));
	return 0;
}